Nozzle skirt for blast guns



April 11, 1950 w. L. KEI-:FER

NOZZLE SKIRT FOR BLAST GUNS Filed Jan. 12, 1948 NN p w z w mw wwPatented Apr. ll, 1950 NOZZLE SKIRT FOR BLAST Walter L.' Kaefer,Hagerstown, Md., assignor' to Pangborn Corporation, Hagerstown, Md.,afeorporation of MarylandA f Application Jaliiiary 12, i948,A serialNo.' 1,88

' 7 claims. (01.51-11) 1- This inventionlrelates tor abrading equipment,and is more particularly concerned with guns fused to' project at highvelocity a stream ofliquid and abrasive material, such as water andsand.

Guns of this type usually comprise a jet disposed in a chamber fordelivering a stream oi liquid at high velocity into a nozzle, andV meansvfor communicating the chamber with a source of abrasive materialwhereby both the liquid and the abrasive material are mixed together inthe chamber and forced out through the nozzle. One of the diicultiesheretofore encountered is the `4factvthat the mixture streaming from thenozzle outlet at high velocity has a tendency to expand and lose densitythereby decreasing the eiciency of the gun and the accuracy with whichthe projecting stream may be utilized in various types of abrading work.

It is an object of the present invention to reverse this undesirabletendency and thereby to maintain the streaming mixture in a concentratedform'.

Other objects and advantages of this invention will be apparent from thefollowing description considered together with the accompanying drawing,in which drawing:

Fig. 1 is a section through the longitudinal axis of a blast gun of thetype mentioned showing an embodiment of my invention disposed thereon.

Fig. 2 is a section along the line 2-2 of Fig. l.

Fig. 3 is an enlarged longitudinal section of a portion of theembodiment of my invention shown in Fig. 1.

Referring with more particularity to the drawing in which like numeralsdesignate like parts, the embodiment illustrated comprises an elongatedtubular 'member or skirt II, the front or discharge end I2 being anelongated conduit through which a stream I3 of liquid and abrasivematerial is projected. The rear or nozzle end I4 is larger than theoutlet end of -vthe nozzle I5 of the gun. The inner Wall of the nozzleend I4 is provided with a group of inwardly projecting ns or ribs I6.These iins are secured to or integral with the nozzle end I 4, and theirinner edges I7 comprise radially facing shoulders to t snugly about theoutlet end of the nozzle I5. Shoulders it are also provided withinnozzle end I4 to engage'the nozzle tip I9 when the latter is properlyinserted in the nozzle end I4, thereby making it easy to dispose theskirt on the nozzle in the proper relative position. The nozzle andskirt .are heldtogether in this relationship by means of a set screwdisposed through the wall of the skirt to"releasably engage the nozzleI5,

'GUN'SQ n A .-,2- .11; substantially as shown. However, other ineens maybe employed 'for-'securing these twomeinbers in position. AThe spacesbetween the fins I6 are open to' the surrounding atmosphere throughopenings 2 i? and they also 'cornmunic'zate withth'e bore 22 of thedischargeend i2'throughpen ings I The bore 22 has a' gradualltaper fromits rear to its forward tip 24, Where the diameter is greater than thatof the nozzle outlet 25. This isa very important featureof the?invention, as will be explained hereinafter-.i `In operation, 'eL-jety26.-*d1spo'sedf-in' fa :chamber 21 projects at high velocity a stream ofliquid under pressure, such as water 28, from a source (not shown)through the pipe 29 into the nozzle l5. An abrasive, such as wet sand30, is led into the chamber 21 through a pipe 3|. The effect of theprojection of the liquid from the jet 26 at high velocity is to create apartial vacuum in the chamber 21, which, in turn, draws the abrasivematerial into the chamber where it is mixed with the liquid andprojected through the nozzle I5. Ordinarily, the stream I3 of mixedliquid and abrasive projecting from the nozzle expands and rapidly losesdensity. The invention reverses this tendency. As the stream I3 passesthrough the bore 22, it induces a flow oi air from the atmospherethrough the channels between the fins I 6. The indrawn air passesthrough the bore 22 and is trapped between its wall and the stream I3passing therethrough. Since the cross-sectional area of the boredecreases toward its tip but is always greater than the nozzle outlet,the trapped air becomes more and more compressed. The pressure createdby this compression tends to maintain the liquid and abrasive stream ina concentrated state.

I claim:

l. A skirt for the nozzle of a high velocity blast gun comprising atubular member having one end adapted to be disposed over the outlet endof the nozzle in radially spaced relation, means for securing the skirton the nozzle, the other end of the skirt being elongated and having abore 'tapering gradually away from the nozzle end to a diameter greaterthan that of the nozzle outlet.

2. A skirt for the nozzle of a high velocity blast gun, said skirthaving a nozzle end and a discharge end, said nozzle end being adaptedto be disposed oye'rithe outlet end of the nozzle in radiallyspacedrelation, means for securing the lskirt and nozzle insaidrelation, the discharge end of the A'skirt being elongated and having aA skirt for the nozzle of a high velocity blast gun,`said skirt `havingvra nozzle end `and a'V discharge end, saidnozzle'end being adapted tobje disposed over the-.nozzle llongitudinal ilns Withinthe nozzle "end,the Vinner edges thereof being adapted to ngage' the nozzle, means forsecuring` the skirt onth'e nozzle against relative 1 movement, thedischarge'end-of the skirt being elongated and havingla b ore graduallytapering to the outlet thereof to'adiameter greater` than that of thenozzle outlet. k 5. A skirt as de ned'by claim 4 having shoulders withinthe nozzle end to abut the nozzle of .the gun when the nozzle and skirtare in a predetermined relative position.

6. A high velocity blast gun nozzle in combination With a skirt having anozzle end and a discharge end, said nozzle end being secured on thenozzle of the gun in radially spaced relation, the discharge end ofthe`skirt beingl elongated and `having a bore gradually tapering to theoutlet 4 thereof to a diameter greater than that of the nozzle outlet.

7. The combination of a blast gun nozzle for projecting at high Velocitya stream of liquid and abrasive material and a skirt therefor, saidskirt having its inlet end disposed on the nozzle, the outlet end of theskirt having a bore gradually tapering to the outlet thereof to adiameter greater than that of the nozzle outlet, said inlet end havingair admission passages therethrough communicating said bore freely withthe ambient atmosphere, and providing for induction therethrough, bypassage of the liquid stream through said bore, of atmospheric air tosheath the stream within the bore, the Walls of said tapering bore beingpositioned throughout their extent to be in spaced relation to theliquid stream as conned by the sheath of induced air squeezed downbetween said stream and bore.

WALTER L. KEEFER.

REFERENCES CITED The following references are of record in the le 0fthis :patent:

l UNITED STATES PATENTS Number Germany Dec. 20, 1913

